Technical Abstract: Teratology, as a scientific discipline, is relatively new and recognition of poisonous plants that cause birth defects in livestock only came to the forefront in the 1950’s and 1960’s. The Veratrum-induced “monkey faced” lamb syndrome and lupine-induced “crooked calf disease”, both studied extensively at the Poisonous Plant Research Lab, were two that elevated the importance of plant-induced birth defects to the forefront. Since that time other plants have been added to the list known to cause birth defects in animals. The ensuing research efforts have characterized many specific teratogenic chemical compounds, determined mechanism of action, described chemical structure activity relationships, and provided the impetus to develop management strategies to improve understanding of the underlying causes and reduce losses to livestock producers. In addition to Veratrum and lupines, poison hemlock, Nicotiana species, locoweeds, Lathyrus, Solanum spp., cyanide-containing plants, and others contribute to the overall losses to the livestock industry from poisonous plants.